Process of recovering sugar from molasses obtained in the manufacture of sugar from sugar beets



P. M. McHUGH. PROCESS OF RECOVERING SUGAR FROM MOLASSES OBTAINED IN THE MANUFACTURE OF SUGAR FROM SUGAR BEETS.

APPLICATION FILED MN. 3. 1919- 1,402,079., Patented J n- 3, 1922.,

LIME MIXER COOLER OVERFLOW WA ST E.

INVENTOR. /J M. Mc Hag/z pairs stares areas rice,

PHILLIP M. MOHUGH, 0F DENVER, GULURADO.

PROCESS OF RECOVERING SUGAR FROM MOLASSES OBTAINED IN THE MANUFACTURE -OF SUGAR FROM SUGAR BEETS.

To all whom it may concern:

a citizen of the United States, residing at Denver, in the county of Denver and State of Colorado, have invented certain new and useful Improvements in Processes of Recovering Sugar from Molasses Obtained in the Manufacture of Sugar from Sugar Beets, of which the following is a specification.

This invention relates to a process of recovering sugar from molasses obtained in the process of manufacturing sugar from sugar beets.

The recovery process herein referred to is that commonly known as the Stefiens House method to recover sugar from the molasses residue of the final crystallization step of the sugar refining process.

It is the object of the present invention to lighten the work required of the filtering devices at present employed in the abovementioned process to separate the liquor from the hot saccharate which as a precipitate is subsequently added to the material treated in the lime mixers of the sugar refining process of which the-molasses is a by-product.

l attain the above-described object by the use of one or more settling devices or gravitational separators commonly known as thickeners in which the solids contained inthe pulp settle out of the liquid and are removed through a discharge opening by the action of rotating rakes or scrapers while the liquid rising out of the precipitate is decanted.

Although thickeners of this type may be employed at other points in the process of recoverin the sugar, it is of particular value after the heating action by which the sugar remaining in solution is precipitated principally as tri-calcium saccharate, commonly termed hot saccharate.

"in the process of recovering sugar from molasses as it is at present performed, filters are employed to separate the liquor from the hot saccharate, and by first permitting the saccharate to settle out of the liquor before it is fed to the filters, a considerable saving in the cost of operating the filters is ehected.

This saving ofoperatin expenses relates more particularly to the lter cloths which by reason of the temperature and alkalinity of the hot saccharate mixture, deteriorate Specification of Letters Patent. Patented J m 3 11922 Application filed January 3, 1919. Serial No. 269,401.

to, pressure filters now generally used for freeing the hot saccharate from liquid, may be 'ellminated and filtering devices of more simple and economical construction used in the place thereof.

Particularly adapted for use in the process are thickeners of the Dorr type which in their simplest form consist of a settling vessel having an overflow for liquid and an outlet for the discharge of the precipitate which is constantly moved thereto across the bottom of the vessel by the rotary movement of a series of rakes or scrapers on a rotatlng upright shaft.

While thickeners having a single settling area, may be advantageously employed in the relation to the other steps of the process herein referred to, it is by reason of increased capacity in ratio to floor space and lowered cost of installation and operation, preferable to use thickeners which by a plurality of superposed settling areas are divided into compartments from which the liquid rising out of the solids is automatically decanted. Thickeners of the Dorr type commonly known as tray thickeners are particularly adapted for this purpose.

In Figure 1 of the drawings is shown diagrammatically a sequence of steps of the above described recovery process in which the thickening action is included;

Figure 2 shows a sectional elevation in outline of a thickener of the Dorr type hereinbefore referred to, and

Figure 3, represents a sectional elevation of a tray thickener of the same type.

n1 Figure 2 of the drawings, the reference numeral 5 designates a settling vessel which is preferably of cylindrical form, 6 an overflow launder at the upper edge thereof, 7 an outlet in the central portion of its bottom surface, and 8 the rakes on radial arms or a rotary shaft 9, which continuously move the material settling on the bottom of the vessel toward the outlet.

The tray thickener shown in Figure 3 l1= sists of a tank which by a plurality of sup-er posed decks or partitions 10 is divided into a plurality of settling compartment 12.,

' j Hall and Rolfe, 2nd edition of 1911, pages The material underitreatment is fed into the upper compartment; the thickened matter which by the scraping action of the series vided with central openings 19 through V which the material is distributed to the different compartments, and these openings may be surroundedbyhpstanding collars 20 for the retention of solids until removed through the pipes 16.

Tray thickeners of the same type but op- I crating somewhat differently from that shown in the drawings may be used to advantage. 'Forexample, the collars 20 and the discharge-pipes 16 maybe eliminated in whichcase the thickened product is'removed from the upper decks through their central 7 hfopjeningsto collect in the lower compartment from which it is discharged as before.

'The Steflens process was devised to recover sugar 1,11 molasses residuum from the main beet sugar refining system. The presh ent Steflens process consists of two steps. 3

First, the'recovery of sugar by the cold process which has been generally practiced for some time, and is" described in Beet Sugar Making and Its Chemical Control, by Y. Nikaido, edition'of 1909, pages. 249 to 255 inclusive; in Beet Sugar Manufacture by 248-251 inclusive and in Beet Sugar Manufacture and Refining, vol. 2 by Lewis F.

which was developed after thefirst step had '40 Ware, edition of 1907, pages 490-501 inclusive. I

The second step of the Stefiens process been in operation for sometime is described briefly in Beet Sugar Making and Its Chemical Control, su ra, page 255', and consists of the so-called teiiens hot process.

Referring'to Fig. 1, the molasses from the 2 main sugar refining'system is first diluted with water to about 12 lBrix and cooled down to about 15 .(see Beet Sugar Mak mg and Its Chemical Control, supra, pa e 249), Powdered calcium oxide is gradual y 7 added, the temperature being maintained at V or slightly below 15 C. Suitable agitation 5 is provided. "A slightly greater quantity of calciumoxide'is addedjthan is required to V precipitate thesugar present as tricalcium saccharate'. The latter compound is insol uble, and whenthe above described action is complete the filteredv liquid will show about 615 Brix (see Beet Su ar Maki and Its Chemical Control, supra page 243% The m xture is next filtered for the recovery of the insoluble trisaccharate, which is finally washed with cold water-while in the filter eonora presses. The filtrate from this operation was formerly considered waste water and discarded, but with the institution of the Stefl'ens hot process it is now further treated as indicated in Fig. 1. My invention relates to this so-called hot process.

The above mentioned filtrate from the socalled cold process is heated to about the boiling point, or as more recent practice has indicated, to about 85 C. Practically all of the remainin sugar in the liquid which is probably in t e form of mono-calcium sac charate (see SugarMaking and its Chemical Control, supra, page 255) is now precipitated as the insoluble tri-calcium saccharate.

continuous rotary suction filters, where the. precipitate of the tri-calcium saccharate is further de-watered and washed with hot water.

The washed precipitate, representin the so-called hot saccharate, isnow com ined with the cold saccharate from the precedin step, and returned to. a point near the hea of the main system for the recovery ofsugar from beets.

The so-called cold saccharate described above, is according to Beet Sugar Making and Its Chemical Controhsupra, page 251, composed principally of diand tri-calcium saccharate. scribed above is according to the same reference, page 255, composed principally o tri-calcium saccharate;

The so-called hot saccharate del Bg employing a thickener as above descri e d to separate the sludge from the I have efiected an important improvement therein, and haveconsiderably lessened the operating expenses which are incident upon the use of filter presses now commonly employed at this stage in the process of beet sugar manufacture. The elimination of pressure filters also results ina saving in labor, and a decrease in the percentage of sugar carried away in the solution in the eminent. I

v Having'thus described my invention what I claim and desire to secure .by Letters- Patent is:

liquid in the so-called Stefiens hot process,

1. In a process of recovering sugar from molasses obtained in the manufacture of sugar from sugar beets, the method of sepa- Add rating calcium sacchara-te from a liquid in intermixture therewith, which comprises continuously introducing the liquid mixture into a container, allowing the solids to settle out of the liquid, continuously overflowing the clear liquid from the upper part of the container, continuously removing the precipitate to a point of discharge by means of a rotating scraper, and filtering the precipitate.

2. In a process of recovering sugar from molasses obtained in the manufacture of sugar beets, the method of separating hot saccharate from a liquid in inter-mixture therewith, which comprises continuously introducing the liquid mixture into a container, allowing the solids to settle out of the liquid, overflowing the clear liquid from the upper part of the container and continuously removing the precipitate to a central point of discharge by the movement of a series of scrapers mounted upon rotating arms radiating from the point of discharge, and filtering the precipitate.

3. The process of recovering sugar from molasses obtained in the manufacture of sugar from sugar beets, which comprises mixing the molasses with lime, cooling the mixture, filtering it, heating the filtrate to precipitate saccharate, continuously introducing the resulting mixture of solids and. liquid into a container, allowing the solids to settle out of the liquid, continuously overflowing the clear liquid from the upper part of the container, continuously removing the precipitate to a point of discharge by a continuous rotary movement of radially disposed scrapers, and filtering the precipitate.

4. The process of recovering sugar from molasses obtained in the manufacture of sugar from sugar beets, which comprises mixing the molasses with lime, cooling the mixture, filtering it, heating the filtrate to precipitate saccharate, introducing the resulting' mixture of solids and liquid into a tank divided into a plurality of superimposed compartments, allowing the solids to settle out of the liquid into the compartments, continuously overflowing the clear liquid from the upper part of each compartment, continuously removing the precipitate to a central point of discharge by means of rotary scrapers, and filtering the precipitate.

In testimony whereof I have afiixed my signature.

PHILLIP M. McHUGI-I. 

